Development Of Powder Mechanical Spectroscopy And Its Application To The Investigation Of Relaxations To Phase-change And Metal-organic Framework Glasses

The mechanical relaxation spectroscopy（also known as dynamical mechanical analysis,internal friction spectroscopy）is the main method to study the dynamical relaxation of solid and soft materials.The mechanical relaxation spectroscopy is widely used in amorphous system,which has a guiding significance for the understanding of the basic scientific problems such as mechanical properties and deformation,thermal stability and crystallization of amorphous materials and developing new amorphous materials.However,at present,the mechanical relaxation spectroscopy equipment has strict requirements on the sample size and material stiffness.It just can be working when the sample size reaches the centimeter level and the material stiffness is in the range of 10²-10⁷N/m.On the other hand,a variety of newly developed amorphous materials with important applications can not meet these conditions.For example,the phase-change memory materials are generally nano scale films;the metal-organic framwork glasses are mainly powder or micron scale particles.Due to the limitation of samples,there are few studies on the relaxation behaviors of these two glassy materials,especially the relationship between the relaxation behaviors and the composition or properties.In this paper,a self-made powder clamp is used based on the traditional commercial dynamic mechanical analysis equipment.It breaks through the limitation of traditional clamps of dynamical mechanical analysis on the size of materials,puts forward the method of powder mechanical spectroscopy,and studies the relaxation behaviors of some important glassy materials.The main works of this paper are summarized as follows:Systematically analyzed,compared and verified with each other of the mechanical relaxation spectra obtained from the test of powder kit and traditional clamps.It is revealed that the powder mechanical spectroscopy after temperature correction is basically consistent with the mechanical spectroscopy obtained by the traditional clamps,which prove the feasibility and reliability of the powder mechanical spectroscopy.The relaxation behaviors of amorphous phase-change and non phase-change memory materials are systematically studied,we found that there were pronouncedβrelaxations in amorphous phase-change memory materials（manifested as excess wings）.It is revealed that the rapid phase transition of phase-change memory material is closely related toβrelaxation.The relaxation behaviors of a series of glassy metal-organic framework materials were measured by powder mechanical spectroscopy.We found a positive correlation between fragility or glass-forming ability and the length of organic ligands,and the maximum fragility（130）of the glassy metal-organic framework material was captured so far.By the powder mechanical spectroscopy,we established the existence of β-relaxations in amorphous[Co（peb）₂]_7n[Hpeb=4-（2-（4-pyridyl）ethenyl）benzoic acid]and[Co₅（pbp）₆]_2n[Hpbp=4-（4-Pyridyl）bibenzoic acid]materials（manifested as pronounced peaks）.After thermal treatment of[Co（peb）₂]_7n glass,the fragility of this glass changed significantly,which revealed the existence of polyamorphism in[Co（peb）₂]_7n glass.The research results of this paper provide a new method for the detection of relaxation behaviors of glassy materials,it is of positive significance to promote the development of glassy physics and material science.